Various devices for locking a vehicle transmission are known to those skilled in the art. Many of these devices, however, are located externally from the transmission housing, such as at the wheels or at the power take off. Many of these devices also have internal cam lever and cog structures that require two clutch collars. The internal cam levers and cog structures, as well as the clutch collars, add cost and complexity to the transmission.
Examples of the prior art devices described above and others include the system shown in U.S. Pat. No. 6,856,880. In this patent an automatic transmission with several forward gears and one reverse gear is taught. The transmission has a parking feature that uses engagement of both the forward and reverse gear trains to stop the transmission. For example, the first gear train and the reverse gear train can be engaged to prevent the output shaft of the transmission from transmitting drive to the wheels. Such an arrangement puts the input and output shafts in a double mesh state to produce a stopping force and causes the transmission to be in a parked state.
The English abstract of JP2002227999 describes a parking lock system for an automatic transmission. Based on the abstract and the figures only, the system comprises a parking gear mounted on a countershaft where the parking gear is engaged with a pawl. The pawl is engaged with structure 92. Structure 92 comprises a gear mounted on a shaft where the shaft is fixed to the transmission case. Structure 92 also comprises a spring loaded member capable of engaging and disengaging the gear with the pawl.
U.S. Pat. Nos. 6,648,093 and 6,691,815 both teach a pawl assembly mounted on a shift shaft which is connected to a gear shift lever. The pawl assembly functions as a transmission parking brake and comprises an actuating lever engagable with a park lock lever. The park lock lever engages with one of a plurality of teeth on a parking gear mounted on the rear output shaft.
In light of the complex and expensive systems of the prior art, it would be advantageous to have a simple brake feature for a transmission. It would also be advantageous to utilize a single clutch collar to reduce the cost and complexity of the transmission.